Luminaires with automated and remotely controllable functionality are well known in the entertainment and architectural lighting markets. Such products are commonly used in theatres, television studios, concerts, theme parks, night clubs, and other venues. A typical product will typically provide control over the pan and tilt functions of the luminaire, allowing the operator to control the direction the luminaire is pointing and thus the position of the light beam on the stage or in the studio. This position control is often done via control of the luminaire's position in two orthogonal rotational axes usually referred to as pan and tilt. Many products provide control over other parameters such as the intensity, color, focus, beam size, beam shape, and beam pattern. Additionally, it is becoming common to utilize high power LEDs as the light source in such luminaires and, for color control, it is common to use an array of LEDs of different colors. For example a common configuration is to use a mix of Red, Green and Blue LEDs. This configuration allows the user to create the color they desire by mixing appropriate levels of the three colors. For example illuminating the Red and Green LEDs while leaving the Blue extinguished will result in an output that appears Yellow. Similarly Red and Blue will result in Magenta and Blue and Green will result in Cyan. By judicious control of the LED controls the user may achieve any color they desire within the color gamut set by the LED colors in the array. More than three colors may also be used and it is well known to add an Amber or White LED to the Red, Green and Blue to enhance the color mixing and improve the gamut of colors available. The products manufactured by Robe Show Lighting such as the Robin 600 LEDWash are typical of the art.
The differently colored LED dies may be arranged on packages in the luminaire such that there is physical separation between each color of LED, and this separation, coupled with differences in die size for each color, may affect the spread of the individual colors and result in inadequate mixing of the different colors along with objectionable spill light and color fringing of the combined mixed color output beam. It is common to use a lens or other optical device in front of each LED package to control the beam shape and angle of the output beam; however, these optical devices may have differing effects for different colors and color fringing or other aberrations may be visible in the output beam. It would be advantageous to have a system where stray light and aberrations are well controlled.
FIG. 1 illustrates a prior art LED lighting system showing two LEDs in a package as may be used in a luminaire. LED 2 and LED 4 may be of differing colors and, due to the different optical properties and construction of the LEDs 2 and 4 produce light beams 6 and 8 that differ in beam spread. The differing beam spreads mean that the light beams from LEDs 2 and 4 will impinge on an illuminated object 18 in such a way that areas 20 and 16 of the object 18 are illuminated by a single LED only rather than the desired mix of both. This results in areas 20 and 16 being colored differently from the central mixed area and appearing as colored fringes. Only two (2) LEDs are illustrated in FIG. 1 for clarity and simplicity. It should be appreciated that the same problem exists with systems incorporating more than two colors of LEDs.
FIG. 2 illustrates a typical multiparameter automated LED luminaire system 10. These systems commonly include a plurality of multiparameter automated luminaires 12 which typically each contain on-board an array of LEDs, and electric motors coupled to mechanical drive systems and control electronics (not shown). In addition to being connected to mains power either directly or through a power distribution system (not shown), each automated luminaire 12 is connected in series or in parallel to data link 14 to one or more control desk(s) 15. The automated LED luminaire system 10 is typically controlled by an operator through the control desk 15. Consequently, to effect this control, both the control desk 15 and the individual luminaires 12 typically include electronic circuitry as part of the electromechanical control system for controlling the automated lighting parameters.
FIG. 3 and FIG. 4 illustrate an optical system used in the prior art to provide a variable beam angle or zoom to an automated LED luminaire. Each LED 50 which may be fitted with a primary optic 52 has an associated pair of lenses 53 and 55. Lenses 53 and 55 may be separate lenses or each part of an array of lenses covering the entire LED array. Lenses 53 and 55 may each comprise a single optical element 56 and 57 respectively. In operation at least one of lens 53 or lens 55 is stationary with respect to LED 50 while the other may move along optical axis 59. In the example illustrated in FIGS. 3 and 4, lens 55 is fixed relative to LED 50 while lens 53 is able to move along optical axis 59. FIG. 3 shows lens 53 in a first position and FIG. 4 shows lens 53 in a second position closer to LED 50. This varying relative position between LED 50, lens 53 and lens 55 provides a beam angle or zoom to the light beam from LED 50. Such systems are often limited in their zoom range by optical problems caused by the color separation and inadequate beam homogenization. They may further be limited by requiring large movements of the lenses.
There is a need for an optical system for an LED automated luminaire which provides improved color homogenization and beam collimation while also providing improved zoom range.